Clinical and basic studies in the diagnosis and genesis of intra- ocular melanomas are proposed. They are predicated on newly developed techniques or in situ, atraumatic sampling of aqueous humor and the subsequent ultra-micro biochemical analysis of Lactate Dehydrogenase isoenzymes and Proteins. The two methods are intended to permit pre- operative differentiation of the malignant and benign forms of such tumors. They afford hope that one of every five such enucleations, now found to be benign by histopathology post-operatively, can be prevented. While enucleations for this reason must continue until proof of biochemical relationship to morphology accrues, there will be concomitant animal studies using heterologous transplantation into rabbits. Such animal investigations with both benign and malignant forms are described with the hope of contributing to the understanding of tumorigenesis and/or prospective non-surgical methods of treating the 4 of every 5 currently destined for enucleation. The sampling and analytical methods have been applied successfully in animals, and permit sustained, non-terminal studies of functional changes both in normal eyes as well as those growing tumors. The latter is attributable to specific patterns which have been determined for the internal ocular tissues, and which reflect themselves in the intra-ocular fluids.